Copper Speciation in Highway Stormwater Runoff as Related to Bioavailability and Toxicity to ESA-Listed Salmon

摘要

The objectives of this study were to (1) identify the effects of site location, storm hydrology, and water quality parameters on the concentration of dissolved copper (Cu(sup 2+)(sub diss)) in Oregon highway runoff; (2) establish an analytical technique suitable for the determination of copper speciation in highway stormwater runoff; (3) compare analytically determined free ionic copper (Cu(sup 2+)(sub free)) concentrations in highway stormwater runoff with modeled concentrations; and (4) develop a qualitative understanding of where and when copper toxicity has the most potential to be problematic for receiving waters. In this study, stormwater runoff from an urban high annual average daily traffic(AADT) site had consistently higher event mean concentrations of measured Cu(sub 2+)(sub diss) and Cu(sup 2+)(sub free) than the non-urban sites with lower AADT. First flush samples displayed consistently higher concentrations of both Cu(sup 2+)(sub diss) and Cu(sup 2+)(sub free). A modified Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-ACSV) technique utilizing salicylaldoxime as an added ligand can be used to determine the speciation of copper in highway stormwater runoff. Analytical results from composite stormwater samples suggest that dissolved copper in highway stormwater runoff is largely complexed by organic matter (typically > 99.9%), and that very little of the copper in stormwater is bioavailable; the concentrations of Cu(sup 2+)(sub free) were generally several orders of magnitudes below levels found to inhibit olfaction in Endangered Species Act listed fish species. Elevated Cu(sup 2+)(sub diss) levels proved to be the greatest indicator of high Cu(sup 2+)(sub free) concentrations. Urban sites with AADT and first flush samples characterized by elevated concentrations of Cu(sup 2+)(sub diss) are of the greatest concern with respect to elevated free ionic copper concentrations.